## How to convert PPB to molarity?

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Dhamnekar Winod
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### How to convert PPB to molarity?

If any water reserve has lead concentration of 20 ppb, how is that = 1 × 10⁻⁷ M Pb²⁺.

My attempt: 20 ppb=x L/1 L solution → x= 20 × 10⁻⁹ L

Now density of

Pb²⁺=11.34 g/cm³ → 20ppb =1.09 × 10⁻⁶ M Pb

Where i am wrong?
Last edited by Dhamnekar Winod on Mon Apr 19, 2021 9:48 am, edited 2 times in total.
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
ChenBeier
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### Re: How to covert PPB to molarity?

20 ppb = 20 mikrogramm/kg = 2*10^-5 g /kg / 207 g/ mol = 0,096 mikromol/kg= 9,66 * 10^-8 mol/kg ~ 1*10^-7 mol/l

For what you need density. It is an aquaeous solution and not solid lead.
Dhamnekar Winod
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Posts: 149
Joined: Sat Nov 21, 2020 10:14 am
Location: Mumbai[Bombay],Maharashtra State,India

### Re: How to convert PPB to molarity?

But mol/Kg and mol/liter are inconsistent units. How did you make unit conversion?
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
ChenBeier
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Location: Berlin, Germany

### Re: How to convert PPB to molarity?

There is no. %, ppm, ppb are parts of a mass unit. For volume you can estimate because 20 ppb is at least nothing. The solution is like water.
Dhamnekar Winod
Sr. Staff Member
Posts: 149
Joined: Sat Nov 21, 2020 10:14 am
Location: Mumbai[Bombay],Maharashtra State,India

### Re: How to convert PPB to molarity?

So, my answer is also correct which is 1.09e-6 M/l. This solution is also like a water
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
ChenBeier
Distinguished Member
Posts: 750
Joined: Wed Sep 27, 2017 7:25 am
Location: Berlin, Germany

### Re: How to convert PPB to molarity?

No, you have a error of factor 10. The unit is also wrong what is M/l in your opinion.
M is mol/l. Not mol/ l^2.
Dhamnekar Winod
Sr. Staff Member
Posts: 149
Joined: Sat Nov 21, 2020 10:14 am
Location: Mumbai[Bombay],Maharashtra State,India

### Re: How to convert PPB to molarity?

Thanks for your guidance. After doing some chemistry work i got the correct answer. 20 ppb =0.2e-7 l = 0.2e-7 kg = 0.2e-7 × 10³ g=200.0 e-7 g ~ 1.0 e-7 M
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]